Semiselective POCE NMR spectroscopy.

A new scheme is proposed to edit separately glutamate C(3) and C(4) resonances of (1)H bound to (13)C, in order to resolve these two signals which overlap at intermediate magnetic fields (1.5 T-3 T), commonly available for human brain studies. The two edited spectra are obtained by combining the individual acquisitions from a four-scan measurement in two different ways. The four acquisitions correspond to the two steps of the classical POCE scheme combined with another two-scan module, where the relative phases of the C(3) and C(4) (1)H resonances are manipulated using zero quantum and double quantum coherence pathways. This new technique exhibits the same sensitivity as POCE and allows the (13)C labeling of C(3) and C(4) glutamate from [1-(13)C]glucose to be monitored separately in the rat brain at 3 T.